Hand charmer: the perfect door handles

Plasma deburring in the automotive supply industry

When a car buyer makes the decision to buy a car made by a premium manufacturer, it is not only the performance and design of the vehicle that have to be right but also the feel. That is particularly true for components that are subject to regular handling such as door handles, for example. However with plastic handles manufactured in pairs by means of injection moulding, when they are subsequently separated from the mould a burr is left behind on the separating edge that is considered annoying by the user. A perfect burrless surface with a clean finish is also required for galvanising and subsequent colour treatment.

In the case of one automotive supplier, the burrs were first of all removed manually using grinding machines. This process turned out to be inefficient and extremely time-consuming. It was also very cost-intensive due to the high number of personnel deployed and the high volume of scrap produced. During the search for alternatives, it was the technically sophisticated method of plasma deburring that was found to deliver the best results. That process needed to be automated. Special machine manufacturers MW-TEC

First published in August 2012 by Mitsubishi Electric based on information provided by MW-TEC GmbH & Co. KG, Velbert, Germany.

and the programming company GISA Automation developed a solution to meet these precise requirements by using Mitsubishi Electric components. The result: a fully automated process where two plasma torches operating in parallel are controlled with a high level of precision by means of the very latest robotic technology.

First of all, small-scale trials were carried out with assistance from Mitsubishi Electric in order to determine the appropriate robotic technology to use. After the test runs produced positive results the decision was made to build the installation. In order to guarantee uninterrupted production during construction, the partners set up a temporary replacement system with help from Mitsubishi Electric.

In the finished system, the MELFA RV 6 SD 6-axis overhead articulated arm robot takes care of surface finishing by guiding the two plasma torches. An additional SCARA RH 12 SDH robot renders the manual reloading of the carrier systems superfluous. A GOT HMI makes the system particularly easy to operate by means of a touch panel and the MELSEC FX3G 60M PLC looks after the whole process of machine control. The system identifies, by means of a light sensor, whether a particular tray contains right or left-hand door handles and passes that information on to the robot controllers which adapt the programs accordingly.

”Unless the customer specifies a particular type of PLC to be used, I prefer to use a Mitsubishi Electric product. The price-performance ratio is unbeatable. Their PLCs not only perform well but are also extremely compact. The same applies to the robot controllers which can be integrated in an installation quite easily without the need for an additional switching cabinet.“

(Dipl.-Ing. Uwe Weyers, Managing Director of MW-TEC GmbH & Co.)

The system can process a tray containing 28 handles in six minutes. Besides significantly reducing the volume of scrap produced, it has also improved performance in terms of time, personnel and cost. The fact that the machine can also operate based on three-shift operation means that it is also highly productive.

Everything Under Control: Robot-assisted Hot-Melt Gluing Station

Smooth teamwork

Economical mass production of door handle systems for the motor industry is only possible with automated manufacturing facilities. MW-TEC is a specialised manufacturer of custom-built machines in Velbert, Germany. In their door handle assembly gluing station, the company uses an agile industrial robot supported by the intelligence of a compact controller, both from Mitsubishi Electric. Integrated in a network, these components help to ensure high product quality and more efficiency on the production line.

Faster, better, more productive – the specifications for the new gluing station were clear: A fast-setting hot-melt adhesive would be used to reduce waiting times and make it possible to proceed to the next assembly step sooner. In turn, this would increase throughput and boost the productivity of the entire production line. The requirements for the gluing process were exacting: The quick-setting hot adhesive needed to be applied evenly across the entire contoured surface of the handle components, in exactly the right quantity and within a very narrow time window. This was a perfect task for a six-axis articulated-arm robot from Mitsubishi Electric.

At the centre of the production line a rotary table transports the handle components and glued assemblies to the individual processing stations. The small MELFA RV-3SB robot, which is fully integrated in the production cell, positions the part correctly beneath the nozzle of the adhesive metering system and then moves it continuously so that adhesive is applied evenly across the curved contours of the surface. After the adhesive has been applied, the robot then places the outer shell on the metal core of the door handle. The entire operation is completed in just 30 seconds, after which the glued components are pressed together briefly by an automatic mechanism. The special adhesive sets almost completely in just two minutes, after which the finished handles leave manufacturing cell via the removal station for further processing.

In addition to improved performance, the MW-TEC engineers also wanted to keep the costs for engineering, installation, commissioning and maintenance as low as possible. They thus chose a standard field bus system to keep the overheads for the assembly station down and to ensure trouble-free communication between the components. Looking for an equally cost-effective and powerful solution for the visualisation and control system, the engineers chose the MELSEC FX3U compact controller and the MAC E300 control terminal, a well-matched duo from Mitsubishi’s wide range of automation components.

The MELSEC FX3U compact controller is the only PLC in this segment that has a master module for Profibus DP, making it possible to configure a very economical solution for all the communications within the production facility via the standard network. The robot, control terminal and remote inputs and outputs are all connected to the controller via the Profibus master module, which supports up to 64 remote field devices.

The components and engineering support were supplied by Otto Kuhmann GmbH & Co. KG, Düsseldorf, which is a partner in Mitsubishi Electric’s Automation Network and a member of the Sonepar Deutschland Group.

"We had no trouble at all configuring this 6-axis MELFA RV-3SB for the task, even though this was our very first project with a Mitsubishi robot.”